<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        * {
            margin: 0;
            padding: 0;
        }
        
        .wrapper {
            width: 100%;
            height: 300px;
            min-width: 200px;
        }
        
        .wrapper>div:nth-child(1) {
            background: red;
        }
        
        .wrapper>div:nth-child(2) {
            background: green;
        }
        
        .wrapper>div:nth-child(3) {
            background: blue;
        }
        
        .wrapper>div {
            width: 33.33%;
            height: 300px;
            float: left;
        }
        
        @media screen and (min-width: 500px) and (max-width: 1000px) {
            .wrapper>div:nth-child(1),
            .wrapper>div:nth-child(2) {
                width: 50%;
            }
            .wrapper>div:nth-child(3) {
                width: 100%;
            }
        }
        
        @media screen and (max-width: 500px) {
            .wrapper>div {
                width: 100%;
                height: 300px;
                float: left;
            }
        }
    </style>
</head>

<body>

    <div class="wrapper">
        <div></div>
        <div></div>
        <div></div>

    </div>

</body>

</html>